Design, synthesis and evaluation of 4-substituted anthra[2,1-c][1,2,5]thiadiazole-6,11-dione derivatives as novel non-camptothecin topoisomerase I inhibitors.

Previously, 4-tosylanthra[1,2-c][1,2,5]thiadiazole-6,11-dione (1) was identified as a novel non-camptothecin topoisomerase I (Top1) inhibitor by structure-based virtual screening. Herein, a series of 4-substituted derivatives were designed and synthesized. Most of them showed potent Top1 inhibitory activity. Their in vitro antiproliferative activity was also evaluated in A549, HCT-116 and ZR-75-30 human cancer cell lines. Compound 8s showed good antiproliferative activity with IC50 of 0.52µM and 0.42µM against HCT-116 and ZR-75-30 cell line, respectively. Top1 unwinding assay and molecular modeling studies rationalized the mode of action of this new class of inhibitors.